1. Field of the Invention
The present invention relates to a method and apparatus for providing a broadcast service to a terminal while maintaining service continuity in a digital broadcasting system.
2. Description of the Related Art
A Digital Video Broadcasting-Handheld (DVB-H) Convergence of Broadcasting and Mobile Service (CBMS) system, which is a type of digital broadcasting system, provides more convenient functions by combining digital TV broadcast services, which have excellent mobile reception performance, with other mobile communication services.
Currently, people can enjoy High Definition TV (HDTV)-class image quality and CD-class audio quality in their homes. However, there is an increasing demand to enjoy TV services of high image quality even while traveling.
DVB-H CBMS, which is a system made for mobile receiving terminals capable of using mobile communication channels, includes a concept of a handover supported in cell-based wireless communications like in a conventional mobile communication system. However, a handover in broadcast networks is distinct from a handover in mobile communication networks that always manage subscribers. More specifically, in mobile communication systems, the network manages individual users, and receives Measurement Reports from the terminals for network management, including a handover. However, in general broadcasting systems, broadcast service providers provide services and contents, but do not manage all of individual users. That is, the service providers send the information for broadcast reception to all users over the broadcast network, but have no user management function. Therefore, the handover in broadcast networks has a specific technical requirement that is distinguishable from that of the handover in mobile communication systems.
FIG. 1 illustrates an architectural model of CBMS, or architecture of a general DVB-H system. Internet Protocol (IP) Datacast over DVB-H involves a collection of entities that work together in order to achieve the required capabilities.
The entities illustrated in FIG. 1 are logical entities, which can be either physically separated or combined into various units, and the logical entities may be merged into one or more physical entities. For convenience purpose, only the interfaces directly associated with the main features of the present invention are illustrated herein.
The system illustrated in FIG. 1 is for Digital Video Broadcasting-Convergence of Broadcasting and Mobile Service (DVB-CBMS), which is one of the mobile broadcast terminal standard organizations. Although the following description will be given in connection with, for example, a notification broadcasting mechanism of DVB-CBMS, a similar operation would also be available in other mobile broadcasting systems with a notification messaging function.
Referring to FIG. 1, a Content Creation (CC) 110 provides broadcast services, which may include a conventional audio/video broadcast service, file (music file or data file) download service, etc. The Content Creation 110, when there is a problem or change in provision of broadcast services, notifies the change to a notification event generator (not shown) in a Service Application (SA) 120.
The Service Application 120 is provided with content data for broadcast services from the Content Creation 110, and generates broadcast service data by processing the content data in a form appropriate for a broadcast network (e.g., in a form of streaming audio/video, movie download, etc.). Further, the Service Application 120 creates standardized metadata needed for an Electronic Service Guide (ESG), and creates accounting information for users. Also, the Service Application 120 receives a notification on the change in broadcast services from the Content Creation 110, delivers a notification event to a notification message generator located in a Service Management (SM) 130, and provides service guide attribute information used for creation of a notification message to the notification message generator.
The Service Management 130 determines a transmission schedule of the broadcast services provided from the Service Application 120, and generates a service guide. The Service Management 130 is connected to a Broadcast Network 140 capable of providing broadcast services, and an Interactive Network 150 capable of supporting interactive communication.
The Service Management 130 manages subscription information for a subscriber(s) intending to receive a broadcast service, service provision information such as information about whether the subscriber has purchased relevant contents, and device information for the terminals that will receive the broadcast service. The Service Management 130 delivers user accounting information to the Service Application 120, and provides the subscription information, the service provision information, the device information, etc., to the Broadcast Network 140 and the Interactive Network 150.
The Broadcast Network 140 is a network that delivers broadcast services. In this specification, DVB-H will be given as an example of the network.
The Interactive Network 150 delivers broadcast services on a one-to-one basis, or exchanges control information related to receipt of broadcast services and additional information in an interactive way, and can be embodied by an existing cellular network such as, for example, a 3GPP Wideband Code Division Multiple Access (WCDMA) network.
A Terminal 160 receives broadcast services, and can connect with a cellular network according to its capability. In the present application, a terminal capable of accessing the cellular network will be considered.
CBMS-x is an interface in the scope of the IP Datacast standard over DVB-H, and X-x is an interface out of the scope of the IP Datacast standard over DVB-H. More specifically, a CBMS-7 interface is an interface from the Service Application 120 to the Service Management 130, and a CBMS-3 interface is used when a message is directly delivered from the Service Management 130 to the Terminal 160 over the Broadcast Network 140. A CBMS-4 interface is used when a message delivered from the Service Management 130 is directly delivered to the Terminal 160 through a dedicated channel to the Terminal 160 over the Interactive Network 150, or through a broadcast channel provided by the Interactive Network 150. A CBMS-6 interface is an interface between the Service Management 130 and the Broadcast Network 140, which is used to establish a transmission path that the Service Management 130 will use in the Broadcast Network 140, or is used as a reception path for event information generated in the Broadcast Network 140. A CBMS-1 interface carries control information of the broadcast network to the Terminal 160, and a control signal channel, called Program Specific Information/Service Information (PSI/SI), corresponds to this interface in DVB-H.
An X-3 interface is used to establish a transmission path to be used between the Service Management 130 and the Interactive Network 150. An X-2 interface is used to establish a transmission path to be used between the Terminal 160 and the Interactive Network 150. An X-1 interface is used to establish a transmission path to be used between the Content Creation 110 and the Service Application 120.
If a user belonging to a DVB-H network has traveled from an existing network to a neighboring network, or has moved from a current IP platform to another IP platform, the ongoing service should be provided to the user seamlessly in the network or IP platform to which the user has moved. A terminal should find the program the user was viewing before the handover, from the network to which the user has moved, in order for the terminal to continuously receive the service. That is, when a transport stream is changed, the terminal should find a transport stream in which the same service is provided, in the network or IP platform to which the user has moved, and when a transmission frequency is changed, the terminal should detect frequency information of the neighboring network or IP platform. Information necessary for the above process may be acquired from PSI/SI provided by a DVB broadcast network. In this case, because the handover procedure and method departs from the scope of the present invention, a detailed description thereof is not provided. For more details, reference can be made to ETSI TR 101 211 Digital Video Broadcasting (DVB); Guidelines on implementation and usage of Service Information (SI).
In the above-described process, a service identifier may play an important role in finding the program the user is viewing. The steps the terminal takes to receive the program even after the handover may also be applied in the same way if the user makes inter-cell movement and inter-subcell movement. In addition, when the network or IP platform to which the user has moved does not support the service the user was viewing before, the terminal checks if there is any alternative service available in that network or IP platform. Here, “alternative service” refers to, for example, a new service that is different in program organization in each region, but of the same genre.
The above-described IP platform, which is a set of IP flows managed by the service providers, represents a harmonized IP address space that has no address collisions. An IP platform may span several transport streams within one or more networks. Several IP platforms may co-exist in the same transport stream. An IP platform is identified by platform identification (id).
Platform id values are divided into two ranges. One range includes platform id values that are globally unique. Another range includes platform id values unique only within the scope of a DVB network. Such an IP platform id is globally and uniquely identified by only combination of both a platform id and a network id. In the specification, for ease of description, the first case that global unique platform id is to be used as an example.
In the current network, each IP platform is independent. The IP flows from different IP platforms are also independent, and their IP addresses have no interrelationship. For example, two IP flows in different IP platforms have the same IP address, but they may be different IP flows because two IP platforms are totally independent.
As described above, there is a problem about service continuity in a digital broadcasting system such as DVB-H CBMS. When the same broadcast service exists in the different IP platforms, the terminal cannot recognize it is the same broadcast service because its IP address in different IP platforms is independent. Therefore, when the terminal changes reception of the broadcast service from a first IP platform to a second IP platform, it cannot continue to receive the broadcast service even though the same broadcast service exits in both of the first and second IP platforms.